[meteorite-list] Two New Lakes Found Beneath Antarctic Ice Sheet

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Jan 26 15:32:52 2006
Message-ID: <200601261917.k0QJH6x23055_at_zagami.jpl.nasa.gov>

http://www.eurekalert.org/pub_releases/2006-01/teia-tnl012506.php

Public release date: 25-Jan-2006

Contact: Ken Kostel
kkostel_at_ei.columbia.edu
212-854-9729
The Earth Institute at Columbia University

Two new lakes found beneath Antarctic ice sheet
    
Ancient water bodies may contain ecosystems adapted to life beneath
more than two miles of ice

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Figure 1: MODIS satellite image showing location of Sovetskaya Antarctic
research station and 90?E Lake in relation to Lake Vostok. Detail of
area in the white box is shown in Figure 2.
------------------------------------------------------------------------

The Earth Institute at Columbia University--Lying beneath more than two
miles of Antarctic ice, Lake Vostok may be the best-known and largest
subglacial lake in the world, but it is not alone down there. Scientists
have identified more than 145 other lakes trapped under the ice. Until
now, however, none have approached Vostok's size or depth.

In the February 2006 issue of Geophysical Research Letters, scientists
from the Lamont-Doherty Earth Observatory, a member of The Earth
Institute at Columbia University, describe for the first time the size,
depth and origin of Vostok's two largest neighbors. The two ice-bound
lakes are referred to as 90?E and Sovetskaya for the longitude of one
and the Russian research station coincidentally built above the other.
The scientists' findings also indicate that, as suspected with Lake
Vostok, an exotic ecosystem may still be thriving in the icy waters 35
million years after being sealed off from the surface.

Geophysicists Robin Bell and Michael Studinger of Lamont-Doherty
combined data from ice-penetrating radar, gravity surveys, satellite
images, laser altimetry and records of a Soviet Antarctic Expedition
that unknowingly traversed the lakes in 1958-1959. The shorelines of the
lakes appeared in satellite images of the region as perturbations in the
surface of the East Antarctic ice sheet. In addition, because the ice is
effectively floating on the surface of the lakes, the ice sheet exhibits
slight depressions over the lakes that appear in radar and laser
elevations.

------------------------------------------------------------------------
Figure 2: Detail of ice surface revealing outline of 90?E lake (center)
and part of Sovetskaya Lake (beneath Sovetskaya research station). Data
from 1958 Soviet study (colored dots) revealed a noticeable drop in the
Earth's gravitational pull above the two lakes. White triangles mark the
locations of smaller lakes beneath the ice.
------------------------------------------------------------------------

Bell and Studinger, along with colleagues from the University of New
Hampshire and NASA, report that the 90?E Lake has a surface area of
2,000km2, which is about the size of Rhode Island, and is second only to
Lake Vostok's 14,000km2 surface area. Sovetskaya Lake was calculated to
be about 1,600 km2. Both are sealed beneath more than two miles of ice.

The lake depths, estimated to be at least 900 meters, were calculated
from gravity data taken during aerial surveys in 2000 and 2001. Because
gravitational force is directly related to mass, a decrease in
gravitational pull over the ice sheet corresponds to a decrease in mass
beneath the ice. "Over the lakes, the pull of gravity is much weaker, so
we know there must be a big hole down there," said Bell.

Their depth, along with the fact that they are parallel to each other
and Lake Vostok, indicate that the lake system is tectonic in origin,
the authors conclude.

Shallow lakes scooped out by glaciers or a meteorite impact can quickly
fill with sediment, and thus are short lived. Lakes created by faulted
blocks of the Earth's crust, however, are deeper and don't fill in as
rapidly. Many of the smaller sub-glacial lakes scientists have
identified so far are believed to be shallow "ephemeral" lakes that were
suddenly sealed off by the ice.

The combination of heat from below and a thick layer of insulating ice
above keeps the water temperature at the top of 90?E and Sovetskaya at a
balmy -2 degrees Celsius, despite temperatures on the surface that can
drop to -80 degrees Celsius in winter. Since the lakes are bounded by
faults, Bell said it is likely the lakes receive flows of nutrients that
could support unique ecosystems. Moreover, laser mapping of the ice
sheet surface by NASA's Ice Cloud and Land Elevation Satellite (ICESat)
revealed that this water-ice boundary, or ceiling, is tilted.

"Since the surface is tilted, we know that the ice sheet changes
thickness over the lake and that will drive circulation in the lake,"
said Bell. "This will provide mixing and distribute whatever nutrients
are in the lake, which is an important component of subglacial ecosystems."

This, along with the tectonic origin of the lakes, supports the idea
that despite climate changes on the surface over the last 10 million to
35 million years, the volume of the lakes have remained remarkably
constant, providing a stable, if inhospitable, environment that may
harbor an ancient and alien ecosystem adapted to life beneath the ice
sheet. However, just how, when or even whether scientists will risk the
possibility of contaminating the lakes to confirm their suspicions
remains the subject of an ongoing international debate.

The study was supported by the Lamont-Doherty Earth Observatory, the
Palisades Geophysical Institute, NASA, and the National Science Foundation.

###

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The Lamont-Doherty Earth Observatory, a member of The Earth Institute at
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information, visit www.ldeo.columbia.edu .
 
Received on Thu 26 Jan 2006 02:17:06 PM PST